Boiler shell assembly

ABSTRACT

A TUBELESS BOILER SHELL ASSEMBLY HAVING HIGH HEAT-TRANSFER CHARACTERISTICS BY REASON OF A NOVEL DISPOSITION OF HEAT-ASSIMILATING AND TRANSFERRING VANES WHICH ARE COEXTENSIVELY ATTACHED TO THE INTERFACIAL HEAT-TRANSFER SURFACE BETWEEN THE FIRE AND THE WATER SIDE OF THE SHELL PROPER OF THE ASSEMBLY.

United States Patent lnventor Everett E. Magnuson Signal Mountain, Tenn.

Appl. No. 840,769

Filed July 10, 1969 Patented June 28, 1971 Assignee Eclipse Lookout Co.

BOILER SHELL ASSEMBLY 14 Claims, 26 Drawing Figs.

US. Cl 122/156, 110/97,122/367 Int. Cl. F221: 7/00,

F23m 9/00 Field of Search 122/155,

[56] References Cited UNlTED STATES PATENTS 1,147,734 7/1915 Junkers 122/367X 2,684,054 7/1954 Carson 122/156X 3,050,041 8/1962 Hale 122/367 Primary Examiner- Kenneth W. Sprague Attorney- Norman 11. Gerlach ABSTRACT: A tubeless boiler shell assembly having high heat-transfer characteristics by reason of a novel disposition of heat-assimilating and transferring vanes which are coextensively attached to the interfacial heat-transfer surface between the fire and the water side of the shell proper of the assembly.

PATENTED JUN-28 |9n sum 1 [1F 4 INVEN TOR WW 0 s w H A A M r w% m m V E PATENTEDQJUNZBIQYI SHEET 2 [1F 4 //V VE/V TOR EVERETT E. MAGNUSON BY Arrorney PATENTEDJUH28|97E 3587531 sum 3 [IF 4 FIG. I5

INVENTOR EVERETT E. MAGNUSON y7W 7KM Attorney PATENTEU JUH28 IBYI SHEET [1F 4 FIG. 20

FIG. 22

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INVENTOR EVERETT E. MAGNUSON By -7 E Attorney BOILER SHELL ASSEMBLY capable of use with a gas or oil fired boiler, as well as with a coal or wood burning boiler. More specifically, the invention is concerned with a tubeless boiler shell which is preferably of cylindrical design and is of double-wall or dual-thickness construction so as to afford an annular water jacket which surrounds the central combustion space with heat transfer taking place through the inner shell wall. Still more specifically, the invention has reference to a novel means for enhancing the heat-transfer characteristics of such a boiler shell by materially increasing the effective area of the heat-transfer surface of the shell. The term boiler shell as employed herein refers to a composite structure including both the outer exteriorly visible shell wall and the inner concentric shell wall which defines the cylindrical interface between the central combustion chamber and the surrounding annular water jacket which is established between the two walls. The term "water heating surface" as employed herein relates to the inner surface of the inner shell wall which is in contact with the products of combustion within the combustion chamber and, by conduction, transfers assimilated heat directly to the water in the annular water jacket.

It is well known that the amount of heat which is transferred from the products of combustion in a boiler to a water heating surface is a function of the temperature difierential between the hot gases and the water heating surface, the area of the water heating surface which is in direct contact with the hot gases, and the velocity of the hot gases as they pass over said surface. The present invention enhances the last two of these recited functions, the-first function being a matter of furnace or burner design. Thus, according to the invention, both the effective area of the water heating surface and the velocity of the products of combustion across this increased surface area are materially increased.

Briefly, in carrying out the present invention, the effective area of the heat-transfer surface is increased by the use of a multiplicity of heat-assimilating vanes which are coextensively welded with a full penetration weld to the inner boiler shell wall on the fire side thereof so that they project into the combustion chamber and lie in the path of the upwardly flowing combustion gases. These vanes may, according to the invention, be variously disposed, but in general, they extend in parallelism and in a longitudinal direction or largely so, and they are approximately of full water jacket height, which is to say that they extend upwards to at least the level of the water in the water jacket. Vane extent and vane thickness constitute a factor that also has been taken into consideration in developing the present invention as will be pointed out in greater detail subsequently. Combustion gas velocity is increased in certain embodiments of the invention by gradually decreasing the distance between adjacent vanes in an upward direction, i.e., so that the distance between adjacent vanes near the burner at the lower end of the boiler shell assembly is greater than near the stack at the top of the boiler shell assembly. It is well known that as a gas becomes cooler, its volume is reduced. Therefore, because the vanes are of full water jacket height, the adjacent pairs of vanes define a series of gas passages which extend from the burner to the stack. Since the distance between adjacent vanes decreases in an upward direction, the cross-sectional areas of such passages gradually diminishes in conformitywith the decrease in volume of the products of combustion as they yield their heat to the vanes and the inner shell wall. In this manner, a strong and unifonn wiping" action of the combustion gases against the entire water heating surface is attained and the heat losses which are present in the upper regions of the combustion chamber of a conventional tubeless boiler shell are obviated.

The provision of a boiler shell assembly of the character briefly outlinedabove constitutes the principal object of the present invention. Other objects and advantages of the invention, not at this time enumerated, will become readily apparent as the nature of the invention is better understood. Additional advantages will be specifically pointed out in connection with the structures from which they accrue.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by the claims at the conclusion hereof.

In the accompanying four sheets of drawings forming a part of this specification, several illustrative embodiments of the invention are disclosed.

In these drawings:

FIG. 1 is a perspective view of a boiler shell assembly embodying a preferred form of the present invention, a portion of the dual-thickness shell wall being broken away in order more clearly to reveal the nature of the invention;

FIG. 2 is a sectional view taken centrally and vertically through the boiler sh'ell assembly of FIG. 1;

FIG. 3 is a top plan view of the boiler shell assembly of F IG.

FIG. 3a is a perspective view of one of the pan-supporting and heat assimilating vanes which are employed in connection with the invention;

FIG. 4 is a perspective view of a deflector pan which is employed in connection with the invention;

FIG. 5 is an enlarged horizontal sectional view taken on the line 5-5 of FIG. 2;

FIGS. 5a and 5b are geometrical diagrams, schematic in their representation, illustrating certain cross-sectional and surface area considerations in connection with the vane structure of the boiler shell assembly of FIGS. 1 to 3, inclusive;

FIG. 6 is an enlarged horizontal sectional view taken on the line 6-6 ofFIG. 2;

FIG. 6a is a plan view of a blank from which one of the vanes of FIGS. 1 to 3 is formed;

FIG. 7 is an enlarged horizontal sectional view taken on the line 7-7 of FIG. 2;

FIG. 8 is a horizontal sectional view taken on the line 8-8 of FIG. 2;

FIG. 9 is a horizontal sectional view similar to FIG. 5 but showing a further modified heat-transfer vane arrangement or structure;

FIG. I0 is a horizontal sectional view similar to FIG. 5 but showing a still further modified heat-transfer vane arrangement or structure;

FIG. 11 is a horizontal sectional view similar to FIG. 5 but showing yet another modified heat-transfer vane arrangement or structure;

FIG. 12 is a fragmentary perspective view of one of the heat-transfer vanes of FIG. 1 1;

FIG. 13 is a perspective view similar to FIG. I but showing an additional modified form of heat-transfer vane arrangement or structure operatively installed in the dual-thickness shell wall;

FIG. 14 is an enlarged sectional view taken on the horizontal plane indicated by the line 14-14 of FIG. 13 and in the direction of the arrows;

FIG. 15 is an enlarged horizontal sectional view taken on the line 15-15 of FIG. 13 and in the direction of the arrows;

FIGS. 16 and 17 are detail sectional views, illustrating schematically certain types of welds that are employed in connection with the invention;

FIG. 18 is a perspective view similar to FIGS. 1 and 13 but showing a still further modified form of heat-transfer vane arrangement or structure operatively installed in the dualthickness boiler shell wall;

FIG. 19 is a fragmentary perspective view, schematic in its representation, illustrating the positional relationship between the heat-assimilating vanes and the deflector pan of the boiler shell assembly of FIG. 18;

FIG. 20 is a sectional view similar to FIG. 2, the view being taken centrally and vertically through the boiler shell assembly of FIG. 19;

FIG. 21 is an enlarged horizontal sectional view taken on the line 21-21 of FIG. 20; and

FIG. 22 is a plan view of a blank from which one of the vanes of FIGS. 18 to 21, inclusive, is formed.

Referring now to the drawings in detail and in particular to FIGS. 1 to 3, inclusive, wherein a preferred form of boiler shell assembly embodying the principles of the present invention is shown and designated in its entirety by the reference numeral 20, the assembly involves in its general organization a composite boiler shell proper 22 (hereinafter referred to simply as the shell) which comprises an outer cylindrical shell wall 24 and an inner cylindrical shell wall 26, the two walls being both concentric and spaced apart and establishing a narrow annular water jacket 28 therebetween. The inner shell wall 26 establishes a central combustion space 30. The assembly 20 is capable of use either as a steam generator or as a water heater with or without modification as required and in the present application it will be regarded as a steam generating unit, the water being admitted to the water jacket 28 through a feed water inlet opening 33. The lower end of the water jacket is closed by means of a base ring 34 having an outer downturned rim flange 36 by means of which the boiler shell assembly may beseated on a suitable heat-generating device (not shown) which may be of any suitable type such as a gas or oil burner, a wood or coal burning grate construction, or the like. The upper end of the annular water jacket 28 is closed by a top ring 38 having a steam outlet opening 40 therein, as well as other openings for performing certain functions in connection with various boiler adjuncts which do not relate to the present invention and, therefore, have been collectively designated at 42. The outer shell wall 24 is provided with a hand hole 44 in radial alignment or registry with a fusible plug 46 which is carried by the inner shell wall 26, the plug being disposed a slight distance below the normal water level of the jacket 28 as is customary in connection with a tubeless boiler of the type under consideration.

It will be understood that the disclosure of the boiler shell assembly 20 herein is somewhat schematic in its representation and many of the essential or auxiliary boiler adjuncts such as a water gauge, hand hole closures or doors, water and steam connections, a safety valve, additional hand hole openings, an exhaust stack and the like have been omitted since they bear no direct relation to the present invention which is concerned solely with enhancing the transfer of heat from the central combustion space which is established by the inner shell wall 26 to the water or other liquid in the annular water jacket 28. Furthermore, the details of the assembly of the composite shell have not been fully illustrated and described herein, suffice it to say that conventional and satisfactory boiler practice is resorted to such as the welding-together of the various meeting edges or surfaces of the shell, including any vertical seam lines which may be present in the shell walls and the use of backing rings such as those shown at 50 for reinforcing purposes wherever required. The usual flush angle ring 52 and hoisting lugs 53 are provided at the upper rim region of the outer shell wall 24.

The general arrangement of parts thus far described is more or less conventional and no claim is made herein to any novelty that is associated with the illustrated annular dual wall boiler shell which establishes a central combustion chamber or space and an encompassing water jacket for reception of feed water, the novelty of the present invention residing rather in the use of a lower annular series of ribbonlike heat-assimilating and heat-transfer vanes 54 and an upper annular series of ribbonlike heat-assimilating and heat-transfer vanes 56, such vanes 54 and 56 being welded in a particular manner to the inner surface of the inner shell wall 26 and being directly exposed to the primary products of combustion passing through the combustion chamber and emanating from the burner or other heat-generating burner or furnace beneath the boiler shell assembly and on which the latter is seated. Several arrangements of such heat-assimilating and heat-transfer vanes will now be described in detail.

Still referring to FIGS. 1 to 3 and 3a, the vanes 54 of the lower series are formed of flat plate stock which preferably is of steel, and are disposed in circumferentially spaced relationship around the outer region of the combustion chamber 30 adjacent to the lower end of the latter. These vanes are welded to the inside cylindrical surface of the shell wall 26 in a manner that will be described presently. Each vane is of appreciable thickness, for example, on the order of three-eighths of an inch in thickness, and is generally of rectangular configuration and of vertically elongated design. The various vanes 54 are equally spaced around the combustion space, extend vertically, lie in radial planes, and have their outer longitudinal edges welded coextensively and intimately to the inner surface of the inner shell wall 26 by a full penetration weld. An example of such a full penetration weld is shown in FIG. 16 and designated by the reference numeral 57. By referring to FIG. 16, it will be apparent that in effecting the weld 57, not only is there an addition of material to the union, but limited portions of the vane 54 and the inner shell wall 26 are fused in the process. The weld 57 of FIG. 16 is effected from one side of the vane 54 during assembly of the boiler shell, but it is obvious that a dual full penetration weld may, if desired, be effected from opposite sides of each vane. A large number of the vanes 54 are employed, the specific number being dependent, of course, upon the size of the boiler shell. Generally speaking, if the vanes are spaced on from 2 to 4 inch centers, satisfactory results for the purposes intended will be attained. The height of the individual vanes may vary within certain limits, but in the illustrated fonn of the invention, these vanes extend approximately one-third of the way upwardly from the boiler shell base, i.e., the base ring 34.

As best illustrated in FIGS. 2 and 3a, each vane 54 is provided with a truncated inner and upper corner region which establishes an inclined pan-supporting edge 58 so that when all of the vanes are welded in position on the inner shell wall 26 as previously described, these edges provide, in effect, a frustoconical seat for the conical lower end region of a relatively deep and generally cylindrical deflector pan 60 (see also FIG. 4). This deflector pan 60 embodies an upper cylindrical sidewall or body portion 62 and a lower conical bottom wall portion 64 which, as aforesaid, rests upon the inclined edges 58 of the various radially disposed vanes 54 and constitutes a deflector shield for directing combustion gases radially outwardly toward the peripheral regions of the combustion chamber 30. When thus in position on the vanes 54, the cylindrical sidewall portion 62 of the deflector pan 60 is concentric with the shell walls 24 and 26 and, in combination with the inner shell wall 26, defines a narrow annulus 66 which constitutes a vertical extension of the combustion space 30 and into which the gaseous products of combustion issuing from the aforementioned burner are deflected. The slant height and slant angle of the lower'conical bottom wall 64 of the pan 60 are such that the circular juncture region between the cylindrical body portion 62 and the bottom wall 64 of the pan 60 lies in the common horizontal plane of the upper edges of the radially disposed vanes 54 as clearly shown in FIG. 2.

The above-described deflector pan and the lower supporting vane arrangement set forth above constitutes a basic arrangement which is common to the illustrated forms of the invention which are shown in FIGS. 1 to 17, inclusive, as well as to certain other contemplated forms not specifically shown or described herein. The various modifications of the invention which are subsequently to be described in connection with FIGS. 1 to 17, inclusive, relate, in the main, to the character and disposition of various series of upper heat-assimilating and heat-transfer vanes, all of which, like the lower series of vanes, are provided for the purpose of effectively increasing the water heating surface of the boiler shell assembly, and also, in connection with certain of the vanes, of enhancing the wiping action of the hot gases against the increased area water heating surface.

Considering now the vane structure of FIGS. 1 to 6a, inclusive, the vanes 56 are equally spaced, insofar as their disposition in the annulus 66 is concerned, around the combustion chamber and extend from the upper level of the lower series of vanes 54 to a level slightly below the normal water level of the boiler shell assembly as indicated by the horizontal dotted line wl (see FIG. 2). Each vane 56, like the vanes 54, is formed of thick plate steel stock and the blank from which the vane is formed is of elongated right angle trapezoidal design as shown in FIG. 6a, the blank being designated by the reference numeral 56b. Each vane of the upper series has its longer right angle side 68 extending vertically and welded to the inner surface of the inner shell wall 26 by a full penetration weld in a manner that will be set forth subsequently. The lower short edge 70 of each vane 56 is equal in length, or slightly longer than, the radial distance between the inner boiler shell wall 26 and the cylindrical body portion 62 of the deflector pan 60 so that the extreme lower region of the vane extends radially, or nearly so, with respect to said inner shell wall 26 and said cylindrical portion 62 as shown in FIG. 7. As the vane gradually widens in an upward direction, it deflects progressively away from the radial or nearly radial plane of its lower edge so that in the extreme upper regions of the vane it approaches or assumes a tangential relationship with respect to the inner shell wall 26 as shown in FIG. 5. In the medial region of the elongated vertical vane, it assumes a secantial relationship with respect to the inner shell wall 26 as shown in FIG. 6, the secant depth decreasing progressively as higher elevations are attained.

The geometrical considerations which are associated with this particular progressive departure of the vanes 56 from generally radial planes in their lower regions to generally tangential planes in their upper regions are illustrated in FIGS. 5a and 5b wherein closed quadrilateral shapes 1.. and U represent the shapes of transverse cross sectionstaken through a pair of adjacent vanes 56 at the lower and the upper ends thereof. In these two views, the vanes 56 are represented by the lines 56, the inner shell wall 26 by the line 26', and the cylindrical portion 62 of the deflector pan 60 by the line 62. The points a, b, c, and d represent the points of intersection of the vanes 54 with the inner shell wall 26 and said cylindrical portion 62 at the lowermost vane level.

In FIG. 5a, the quadrilateral shape L assumes a generally rectangular appearance with four approximately equal sides ab, bc, ed and do. The area of this shape is thus at its maximum, it being understood, of course, that the shape represents the shape of the entrance opening for combustion gases entering the passage between two adjacent vanes 56 and confined between said inner shell wall 26 and said cylindrical portion 62. In FIG. 5b, the quadrilateral shape U assumes an almost triangular configuration, considering the fact that although there are four sides, the sides a'd' and d'c' are nearly in alignment. Because of the gradual upward and outward taper of the vanes 56 as shown in FIG. 6a, the lengths of the sides ab' and c'd'are greater than the lengths of the sides ab and cd while the sides ad and b'c remain the same as the lengths of the sides ad and be. Since each pair of adjacent vanes 56, in combination with the intervening portions of the inner shell wall 26 and the cylindrical portion 62, establishes a generally vertically extending passageway for the upward flow of the hot gaseous products of combustion emanating from the burner or furnace beneath the boiler shell assembly 20, the variable wall inclination of this passage as previously described is such that a wide entrance opening (represented at L in FIG. 5a) leading from the burner or furnace beneath the boiler assembly shell exists at the bottom of this passageway, while a comparatively narrower exit opening (represented at U in FIG. 5b) exists at the top of the passageway. Not only this, but the surface area with which the products of combustion are in direct contact at the bottom of the passageway is appreciably greater than the surface area which they traverse at the top of the passageway.

Because of the fact that the volume of a gas is a function of its temperature, ordinarily in any passageway of uniform cross section which is used as a passageway for hot gases, the gases yield up heat previously to the walls of the passageway as they pass through the latter. Thus, near the exit opening of the passageway, their volume has become decreased, and because the cross-sectional area of the passageway does not vary, their velocity also decreases proportionately. In the present instance and according to the form of the invention shown in FIGS. 1 to 6, inclusive, the reduced-volume gases in the upper region of the various passageways between adjacent vanes 56 not only are confined in a smaller space so that their velocity is not reduced, but they make contact with a larger vane area. Thus, their velocity is not diminished and at the same time they make effective wiping contact with a greater area of surrounding metal. In this manner, their heat-transfer factor is greatly enhanced. Additionally, from the point of view of heatconduction, as these hot gases pass upwardly in the passageways between adjacent vanes 56, the efficiency of the various vanes in conducting heat from the combustion chamber extension 66 above the combustion chamber proper 30 through the inner shell wall 26 to the feed water within the water jacket 28 is also enhanced because of the coextensive full depth penetration welding of these vanes to such wall.

It is to be noted at this point that the use of relatively thick vanes 56 in the upper regions of the shell and relatively thick vanes 54 in the lower regions of the shell assures a long-lasting vane construction without detracting in any way from a good heat-transfer factor. The full depth penetration welding of the vanes to the inner shell wall 26 insures a rapid conduction of heat from these vanes to the water in the feed water jacket 28 so that the thick vanes dissipate their heat to the water as fast as this heat is assimilated or absorbed from the products of combustion by the vanes. It is well known that the larger a heat-dissipating or a heat-assimilating area, the greater will be the total amount of transferred heat, either radiated or absorbed and then conducted away. For this reason, it is common practice to increase a heat-radiating or heat-absorbing surface by the use of a multiplicity of fins, as in the case of a baseboard radiator, for example. However, in the present instance, the use of thin heat-absorbing fins which are directly exposed to the hot products of combustion would be impractical because such fins would rapidly burn out due to their inability to transfer their absorbed heat to the water in the water jacket 28 at least as fast as this heat is assimilated thereby. Full penetration welding of relatively thick vanes on the order of three-eighths of an inch has been found to be satisfactory in that, under all normal conditions of boiler operation, heat conduction through the inner shell wall 26 is maintained substantially equal to heat assimilation by such vanes. In general, it may be stated that the cross-sectional area of the vanes 56 is such that the heat assimilated by the latter will be conducted to the inner shell wall 26 at a rate adequate to prevent the vanes from reaching oxydizing temperatures.

The full penetration weld which is effected on each of the vanes 56 is schematically illustrated in FIG. 17. Adjacent to the bottom of each vane 56, a welding operation of the general type shown at 57 is employed, and as the angularity of the vane increases during upward progression of the welding operation, the character of the weld is varied gradually until, adjacent to the upper end of the vane, the weld assumes the form shown at 69. Thus, at no point along the weld line is there a void which would detract from the heat transfer characteristics of the vane.

All of the vanes 56 of the upper series of vanes are thus welded in a progressive manner around the circumference of the inner shell wall 26. However, in order to afford a clearance region for welding of the last vane 56 in position, a void is left between the first welded vane and such last welded vane and a radial vane 56a is finally welded in position within the void and applied to the shell wall 26 by a weld such as the previously described weld 57. Due to the relatively large amount of labor which is required during manufacture of the boiler shell assembly 20, especially in effecting a full depth penetration welding of the vanes, it is essential that the water level in the jacket 28 does not fall appreciably below the uppermost level of the vanes 56. For this reason, and in order to prevent the vanes from overheating, the fusible plug 46 is disposed slightly below such uppermost level.

Considering now various other forms of vane structures and arrangements of vane-distribution in the upper region of the boiler shell assembly immediately above the lower radial vanes 54, it is contemplated that elongated flat upper radial vanes 156 which, throughout their entire length, lie in truly radial planes with respect to the boiler shell as shown in FIG. 9 may be employed in place of the previously described vanes 56 which range from radial in the lower regions thereof to tangential in the upper regions thereof. These radial vanes 156 are of elongated rectangular design and have their outer vertical edges welded by full penetration welds 157 to the inner shell wall 126 along vertical weld lines. In FIGS. 8 and 9, as well as in FIGS. 10 to 21, inclusive, wherein further modified forms of the invention are shown, and in order to avoid needless repetition ofdescription, similar reference numerals but of higher orders have been applied to the corresponding parts as between these views and FIG. 5. In all of the modifications, the involved vanes are formed of plate steel stock similar to that from which the vanes 56 are formed and they have their outer edges welded by full penetration welds to the inner shell wall, the vanes bridging the distance between such wall and the main body portion of the deflector pan.

In FIG. 10, the vanes 256 of the upper series of vanes are flat and rectangular and assume secantial planes with respect to the cylindrical body portion 262 of the pan 260. Varying secant angles are contemplated, the illustrated angle being on the order of 45 from a radial plane extending through the horizontal axis of the pan. All of the vanes 256 assume a secantial relationship except one vane 256a which is disposed in a radial plane. All of the heat-transfer vanes 256 are installed in position on the inner shell wall 226 by a manual welding operation and in welding the last vane 256 in osition, it is necessary that there be adequate access thereto for welding purposes. Therefore, this last vane is positioned sufficiently far from the first welded vane 256 to afford such access. Thereafter, the radial vane 256a is applied and the inclination of the last vane 256 is such as to afford access for welding the vane 2560 in position.

In FIGS. 11 and 12, the vanes 356 are similar to the vanes 156, which is to say that they are of elongated rectangular design. However, in order substantially to increase their heatassimilating surface area, the opposite sides of these vanes are provided with respective series of grooves or serrations 359 which may extend in any desired direction but which in the illustrated form extend vertically.

In FIGS. l3, l4 and 15, the vanes 556 of the upper series of vanes are similar to the vanes 56 of FIGS. 1 to 3, inclusive, but

. they are differently positioned within the annulus 566 which exists between the body portion 562 of the deflector pan 560 and the inner shell wall 526. Instead of being welded at their outer edges along vertical lines to the inner cylindrical face of the inner shell wall 526, the vanes 556 are welded along spiral lines, utilizing full penetration welds which gradually effect a transition from the type of weld which is shown at 557 in FIG. 15 at the lower ends of the vanes to the type of weld which is shown at 569 in FIG. 14 at the upper ends of the vanes. The vanes 556 are so deformed or displaced out of the flat plane of the vase blanks that vane-convergence in their upper regions is effected, the transition being from a radial disposition in the lower regions thereof to a tangential disposition in the upper regions thereof. Thus, the area of the outlet openings of the passageways between adjacent vanes in the vicinity of the stack is appreciably less than the area of the inlet openings of such passageways in the vicinity of the burner or other heatgenerating unit beneath the boiler shell assembly. The vanes 556, therefore, perform the same function as the vanes 56, namely, to increase the overall heat transfer area and also to maintain high gas velocity in the upper region of the boiler shell assembly. Because the combustion gases are obliged to flow through spiral passageways between adjacent vanes 556, their total path of travel from the furnace to the stack is appreciably greater than is the case where the passages are substantially longitudinal as is the case in connection with the vanes 56 and the passageways established thereby.

It is to be noted at thism that in connection with the various forms of the invention thus far described, the deflector pans 60, 160, 260, 360 and 560 are capable of removal bodily from their associated boiler shell assembly for replacement purposes or repair by the simple expedient of hoisting them vertically out of their nested position within the composite shell proper 22, 122, 222, etc., as the case may be. Since the conical bottom walls of such pans rest loosely upon the lower series of vanes, and since the-sidewalls of the pans are not secured to the inner edges of the encompassing vanes, these pans may be slid vertically from the shell assembly by utilizing a suitable hoist or the like.

In FIGS. l8, 19, 20 and 21, a further form of the invention is shown, this form being one of the preferred forms. As clearly shown in FIGS. 18 and 20, the dual-wall boiler shell proper 622 remains substantially the same as the composite boiler shell proper 22 in the form of the invention shown in FIG. 1 as also do the lower series of vanes 654 which are radially disposed and which serve to support the deflector pan 660. In this latter form of the invention, however, the vanes 656 of the upper series are formed from rectangular blank stock as shown at 656b and they have their outer edges welded by a full penetration weld to the inner shell wall 626 and along vertical weld lines. As is the case in connection with the vanes 56 of the boiler shell assembly of FIG. 1, the vanes 656 extend radially with respect to the inner shell wall 626 to which they are welded in the lower regions of the vanes, whereas in the upper regions thereof the vanes extend tangentially with respect to such wall. The gradual transition of the inclination of the vanes 656 results in a change in the character of the weld lines so that in the lower regions of the vanes, the welds resemble the welds 57 of FIG. 16 while in the upper regions the welds resemble the welds 69 of FIG. 17, there being a gradual transition between the two forms of welds.

Because of the fact that the vanes 656 are formed from rectangular blank stock, the gradual upward deformation thereof which is required to make the transition from radial planes to tangential planes as described above, requires that the sidewall or body portion 662 of the deflector pan 660 be of conical design, the slant angle of the cone being small and on the order of only a few degrees, for example, 8 to 10. In this way, continuous tubular passageways which become gradually narrow in an upward direction are provided for the flow of combustion gases upwardly between the body portion 662 of the deflector pan and the inner shell wall 626 of the composite boiler shell proper 622. The conical bottom wall portion 664 of the deflector pan 660 remains sharply conical as is the case in connection with the bottom wall portion 64 of the deflector pan 60 of the boiler shell assembly 20 of FIG. 1 so that the pan in its entirety may be supported on the truncated upper inner comer regions of the lower series of vanes 654. As is the case in connection with the pan 60, the pan 660 is capable of being readily hoisted from the boiler shell assembly for purposes of inspection, repair or replacement. The fact that both the bottom wall 664 and sidewall 666 are of conical design greatly facilitates both removal and replacement operations.

It is to be noted at this point that in FIG. 18, certain of the upper vanes 656 at the left-hand side of the view have been omitted in the interests of clarity in order that the transition from a truly radial vane direction to a tangential vane direction with respect to the slightly conical sidewall portion 662 of the deflector pan 660 may be clearly visualized, while at the same time the vertical disposition of the outer edges of the vanes 656 will be apparent. Similarly, in FIG. 19 which is purely schematic in its representation, there is an omission of vanes while at the same time some of the illustrated vanes 656 are shown in their free state and detached from the inner boiler shell wall 626, the representation being such as to show merely the angular vane disposition with respect to the tapered sidewall portion 662 of the deflector pan 660.

The principle of operation of the form of the invention which is shown in FIGS. 18 through 21 remains substantially the same as that form of the invention which is shown'in FIGS. 1 through 7. In the earlier described form, the passageways between adjacent vanes 56 are tapered in an upward direction by reason of the use of vanes which are formed from flat plate metal stock so as to have trapezoidal configurations which make line contact with two concentric cylindrical surfaces, namely, the inner surface of the inner shell wall 26 and the outer surface of the cylindrical body portions 62 of the deflector pan 60. In the later described form of the invention, the passageways between adjacent vanes 656 are tapered by reason of the use of vanes which, similarly, are formed from flat plate stock but which are originally of rectangular configuration and which, when installed in the annulus of the boiler shell assembly 620, make line contact with the inner cylindrical surface of the inner shell wall 626 and the outer slightly tapered or frustoconical surface of the body portion 662 of the deflector pan 660. in both cases, the reduction in the volume of the flowing combustion gases which pass upwardly between the inner shell wall and said body portion of the deflector pan incident to heat losses in these gases is compensated for by the tapered passage walls so that a substantially uniform wiping" action by these gases on the surrounding heat-transfer surfaces is maintained.

The invention is not to be limited to the precise arrangement of parts shown in the various views of the drawings and described in this specification as numerous vane configurations and vane placements are contemplated. For example, any of the vanes 56, 256, 456, 556 and 656 in the upper series of vanes may be of serrated design as is the case with the vanes 356. Similarly, any of the vanes in the lower series may likewise be serrated if desired. Furthermore, although the present invention has been described herein in connection with a water-heating boiler which may or may not convert the feed water into steam, it is to be understood that the present invention may, if desired, be used, with or without modification as required, for the heating of liquids or chemicals other an aqueous liquids.

I claim:

1. A boiler shell assembly comprising a cylindrical dual thickness open-ended boiler shell including concentric inner and outer shell walls establishing an annular water jacket 'therebetween for a supply of feed water and a central combustion chamber within the inner shell wall through which hot combustion gases are adapted to pass upwardly, and a series of elongated narrow ribbonlike heat-assimilating and heattransfer vanes formed from flat plate metal stock, disposed in said peripheral regions of the combustion chamber in closely spaced circumferential parallel relationship, and extending in an upward direction from the lower region of the chamber to the upper region of said chamber, said vanes having their outer edges welded coextensively by full penetration welds to said inner shell wall and projecting generally inwardly of the combustion chamber and into the path of combustion gases flowing upwardly through said chamber, a relatively deep deflector pan fixedly disposed in said combustion chamber and having a sidewall portion disposed in close proximity to the inner edges of said vanes and, in combination with the inner wall, establishing an annulus within which the vanes are confine'd, and an inverted conical bottom wall portion disposed below the level of said vanes, and a second series of similar vanes similarly welded to said inner wall below the level of said sidewall portion of the deflector pan and substantially coextensive with the vertical confines of said conical bottom wall portion. I

2. A boiler shell assembly as set forth in claim 1 and wherein the vanes of said second series are of greater radial extent than the radial width of said annulus and project below said conical bottom wall portion in supporting relationship.

3. A boiler shell assembly as set forth in claim 1 and wherein the inner edges of the vanes of the first series of vanes are disposed in close proximity to the cylindrical sidewall portion of the deflector pan so that adjacent vanes, in combination with said sidewall portion and the inner shell wall, define a series of individual and generally upwardly extending passages for the upward flow of the combustion gases.

4. A boiler shell assembly as set forth in claim 3 and wherein the thickness of the plate stock from which the vanes of each series are formed is on the order of three-eighths of an inch.

5. A boiler shell assembly as set forth in claim 1 and wherein the vanes of both series of vanes are planar and lie in radial planes with respect to the axis of the shell.

6. A boiler shell assembly as set forth in claim 3 and wherein the vanes of said second series of vanes are planar and lie in radial planes with respect to the axis of the shell, and the vanes of the other series of vanes are planar and lie in secantial planes with respect to the circumference of the sidewall portion of the deflector pan.

7. A boiler shell assembly as set forth in claim 3 and wherein the vanes of the first-mentioned series have their outer edges welded to the inner shell wall along parallel vertical weld lines.

8. A boiler shell assembly as set forth in claim 7 and wherein the vanes of the first-mentioned series have their lower edges extending in radial planes with respect to the axis of the shell and are progressively deflected in an upward direction in such a manner that the upper edges of the vanes lie in substantially tangential planes with respect to the sidewall portion of the deflector pan, whereby the cross-sectional area of said passages decreases in an upward direction.

9. A boiler shell assembly as set forth in claim 3 and wherein the vanes of the first-mentioned series have their outer edges welded to the inner shell wall along parallel spiral lines.

10. A boiler shell assembly as set forth in claim 3 and wherein the vanes of the first-mentioned series have their outer edges welded to the inner shell wall along parallel spiral lines, while the outer edges of adjacent vanes of said first-mentioned series converge in an upward direction so that the individual passageways decrease in transverse cross section in an upward direction.

11. A boiler shell assembly as set forth in claim 3 and including, additionally, a fusible plug extending through the inner shell wall a slight distance below the level of the upper ends of said first-mentioned series of vanes.

12. A boiler shell assembly as set forth in claim 3 and wherein the vanes of said second series are generally of vertically elongated rectangular configuration and have their upper inner comers truncated on an angular bias conforming to the slant angle of the bottom wall portion of the deflector pan, and wherein said corners, considered collectively, constitute a frustoconical seat for the deflector pan.

13. A boiler shell assembly as set forth in claim 3 and wherein the number of vanes in the two series are equal, and wherein the upper edges of the vanes of the second series are disposed in coextensive meeting relationship with the lower edges of the vanes of the first-mentioned series of vanes.

14. A boiler shell assembly as set forth in claim 2 and wherein said deflector pan is loosely confined in said combustion chamber by the inner edges of the vanes of said first series and is supported on the upper edges of the vanes of the second series, whereby the pan is removable from the combustion chamber by sliding the same upwardly therefrom. 

